Method of making current-collector rings



C. B. MILLS. METHOD OF MAKING CURRENT COLLECTOR RINGS.

APPLICAT ON FILED AUG 10 191 1,3 3;3,564:, I Patented Oct. '11, 1921.

WITNESSES: 7 II\;IVEN 'ChesferB/Y/ JZWMZO LW/ composite type which shall be stron Methods .'uN1 Eo STATES PATENTLOFFICE.

onus-rm B. mus; or mar mexnnsrom, rmmsnvmm, assmnonro' wnsrme- HOUSE {ELECTRIC l: MANUFACTURING COMPANY,

Specification of Letters Patent. Patentd Oct, 11, 1921;

Application filed August 10, 1918. Serial Io. 249,846.

To all whom it concern:

Be it known that I, CHESTER B. MILLS, a citizen of the United States, and a resident of East McKeesport, in the county ofAllegheny and State of Pennsylvania, have invented a new and useful Improvement in of Makin Current-Collector Rings, of which the f0 lowing is a specification.

My invention relates to dynamo-electric machines and particularly to current-collector rings for use thereon, and it has for its object to provide a collector ring of thg an durable in construction, be possessed 0 good wearing properties, be of good conductivity and be relatively inexpensive to manufacture.

Heretofore, it has been customary to either construct the entire collector ring of an alloy or to mountahea'vy cast copper ring upon a supporting spider member. An alloy ring is objectionable-4M the, reason that the materials of whichit is composed'tend to segregate themselves, thus causing different degrees of hardness at different points of the ring which result in non-uniformity ofwear. Also, during the-casting operation, the reaction of the metals upon one another produces a gas the escape of which produces pin holes in the metal that usually contain rapidl Furthermore, the commonly employed alloys, such as a combination of copper, lead and tin, have only approximately 30% of the conductivit of rolled copper, and the conductivity of a contact between a carbon brush and an alloy ring is much lower than the conductivity of a contact between a similar brush a d acopper ring.

A heavy cast copper ring mounted on. a

supporting spider. is objectionable on account of the fact that it is soft, open grained, and very expensive. By my invention, I provide a collector I ring which is equal, in every respect, .to a

heavy copper ring mounted, on a supporting spider and costs approximately 25% as muc In the accompanying drawin Figure 1- I a collector ring constructed in accordance with my invention, and Fig. 2 is-a similarview of a portion of the machine engaged in'manufacturing the same.-

metal is made harder, and the together wit which is cut into rings of the desired width and placed between rollers 6 and 7 of a metal rolling machine as shown in Fig. 2. These rings may also be formed by piercing and expanding a'slug cut from a bar. The roller 6 is driven and the roller 7 is merely an idler. so as to reduce its cross section, thus hardening it and. causing the grain of the metal to extend in a circumferential direction. The ring is then shrunk on, or otherwise attached to, the cast-iron supporting member 2 which is afterward mounted upon the supporting hub 3.

- In practising'my invention, I have found that a cast copper ring, mounted upon a supporting member, may be used. However, it isobjectionable en account of the fact that the copper casts wlth an open grain, and is,

the brushes, and that thetensile strength of cast cop er is very low. Furthermore, the conductivity of cast co per is onlyapproximately. 80% of that o worked copper.

rolling the cast On the other hand, b copper ring, the pin ho es are closed, the

copper isdisplosed circumferentlally, which,

ring is frequently broken, since'the metal is a conrona rrou or PENNSYL- METHOD or iuxme ovum-mums RINGS.

The. ring is then rolled, or worked,

I Referring more particularly to the draw- 9o small particles of carbon from the brushes and, in turn, cause rapid wearing away of ain of the l the fact that the metal is compressed by the rolling operation, greatly, mcreases'the tensile strength of the ring, and produces a very good wearing surface.

copper mounted on a supporting ring of cast iron, the copper ring may be replaced by a rolled ring of brass or ,some other good conducting material, and the cast iron supportingrmg may be of steel or even of .micarta, the only essential features of the supportinp ring being strength and rigidity.

While have shown one form of my invention and described in detail one application of the same .it will be obvious to those skilled in the art that it is not so limited but is subject to Various minor changes and modifications Without departing from the spirit thereof, and I desire, therefore',that

only such limitations shall be placed theregrain is not properly cirupon as are imposed by the prior art or are specifically set forth -in the appended claims.

I claim as my invention:

1. The method of making a collector ring comprising casting a. metallic cylinder, Working the metal of said cylinder and attaching said cylinder to a centrally disposed body portion.

2. The method of making a collector ring comprising casting a copper cylinder, rolling the metal of said cylinder to produce a circumferential grain therein, and shrinking said cylinder on a cast iron central body portion.

3. The method of making a collector ring comprising casting a metallic cylinder and Working the metal of said cylinder so as to produce a circumferential grain therein.

In testimony whereof, have hereunto subscribed my name this 31st day of July,

CHESTER B. MILLS. 

